Wax impregnated glass fabric liner and gasket seal



E. E. LAUER Nov. 2, 1943.

WAX IMPREGNATED GLASS FABRIC LINERl AND GASKETVSEAL Filed June 2. 1939@A 1. '.'AVIAIIIIIIIIJ'IIIIIIIIA mrc Patented Nov. 2, 1943 WAXIMPREGNATED GLASS FABRIC LINER. i AND GASKET SEAL Ethan E. Lauer,Rahway, N. J., assigner to Merck & Co., Inc., Rahway, N. J., acorporation ot New Jersey Application June 2, 1939, Serial No. 277,103

3 Claims. (Cl. 288-34) This invention relates to certain new and usefulimprovements in a composition of glass cloth and wax, the purpose ofwhich is to provide seals or gaskets between elements of containers,apparatus, equipment and the like which are used for containing and/ortransporting concentrated acids and other corrosive liquids andsubstances, especially those which should be maintained in a high stateof purity such as acetic, formic, hydrochloric, nitric and sulfuricacids.

Owing to the corrosive nature of strong mineral acids, such ashydrochloric, nitric and sulfuric, apractically insurmountablediiilculty has been experienced in effecting a satisfactory sealing oftheir containers. A common means hitherto employedA has been through theuse of glass or ceramic Stoppers, the sides of which have been grounddown so as to cause the Stoppers to flt within the container necks toform liquid-tight Joints. Even with such ground Stoppers, it has beennecessary to smear the ground surface of the stoppers with a grease inorder to effect a liquid-tight and yet removable seal. The cost ofgrinding the stoppers, the frequency of leakage resulting fromimperfectly ground Stoppers, the contamination of the container contentswith grease from the stopper, the necessity of using some lute to holdsuch stoppers rigidly in position during the transit of containers, andthe frequent freezing of ungreased or insufliciently greased stopperswithin the container necks, have been serious disadvantages.

In the course of extensive experiments it has been found that asbestos,a natural, mined subF stance, usually contains undesirable reactiveimpurities, such as compounds of iron. Though these impurities are notacted upon by many chemicals and may be without adverse effects in theutilization of the products of the art where slight or even moreappreciable contamination is of no technical or commercial consequence,such impurities in asbestos are highly objectionable if the lattershould be applied as a constituent of a closure liner for containers ofconcentrated chemically pure acids.

Coating of asbestos with an acid-resistant substance, in an attempt topreclude the action of acids and other chemicals on the reactiveimpurities in the asbestos, is an unreliable expedient, because inevery-day practice a complete coating is not always attainable.

Glass can be made by specification to be resistant to the action of mostmineral acids, and hence it might appear that the ideal liner for aclosure would consist wholly of such glass. However, glass is normally abrittle material, and no means have been previously known by which toendow a closure lining with the acid-resistant xproperties of glass andat the sarne time to produce a soft resilient, liquid-proof liningmaterial which will be devoid of all contaminating effects uponconcentrated pure mineral acids. y

Glass fibers can b e made long, round, smooth, and altogether suitablefor the construction of a closely-woven, tight fabric, withoutreinforcements of cotton or metallic wires, or other such materials.

However, applicant has found that neither a glass fabric nor a felted ormatted agglomeration of glass fibers is alone capable of providing anon-porous lining material. Applicant has extensively experimented withglass fabrics and felted or matted glass fibers, without adding theretoany lubricating and sealing agent, and it has been found impossible toproduce a liquidproof lining material from any of them because of theirinescapable porosity, however tightly woven the glass fabric, or howeverclosely felted ormatted the glass fibers may have been. He has found,further, that this porosity cannot be overcome by the exertion ofclosure pressure upon the glass fibers of a piece of glass fabric orupon a layer of felted or matted glass fibers placed upon the rim of themouth of a liquid container. The art has so far failed to produce aliquidtight lining material consisting solely of glass fibers capable ofwithstanding such pressure, for thelatter inevitably destroys thestructure of the unprotected glass fibers.

This applicant has discovered that glass bers, in order to aid in theprovision of a perfect seal under screw-cap closure pressure at the rimsof the mouths of containers, for instance, need to receive aninter-lubricating agent which must have the function of perfectlyfilling spaces between or among the glass fibers and, in addition, mustpreserve the purity or the original state of the acids or othercorrosive substances with which that agent may come in contact.

It is therefore a primary object of this invention to provide thecombination of a lubricating and sealing agent and a fabric made frompure glass which will be generally acid-resistant and devoid ofdiscoloring and other contaminating effects on acids, and which at thesame time will provide a liquid-tight closure material.

Another object of the invention is to produce a lining materialconsisting essentially of tightly woven glass fabric impregnated with awax having definite properties, in order to provide a lining or gasketmaterial which will be impervious to the contents of containers;resistant to the corrosive action of concentrated mineral acids or ofdry or moist chemical substances or compounds; devoid of discoloringeffects upon such acids or substances or compounds; sufficientlyresilient to eilect a positive seal when placed within, and tightened bypressure of, a suitable closure; and capable of repeated application byvirtue of its physical properties, structure, and sealing capacity.

It is a further particular object of this invention to utilize a certaintype of construction of tightly woven glass cloth which willsatisfactorily provide a supporting structure for certain acidresistantwaxes in certain proportions, so that the product will be serviceable asa liquid-tight lining material of strong pure acid containers.

With the above and other objects in view that will become apparent asthenature of the inventionv is better understood, the same consists inthe novel form, combination and arrangement of y parts hereinafter morefully described, shown in the accompanying drawing and claimed.

In the drawing, of which the figures are merely diagrammatically andillustratively represented: Figure 1 represents the untreated wovenglass fabric itself Figure 2 represents that woven glass fabric having awax content of about 40 .percent Iby weight;

Figures 3 and 4 are different views of the more `fully impregnated andexternally coated glass fabric; l Y

Figure represents a cross-section. considerably diagrammaticallyenlarged, to show the upper and lower layers of wax and the waximlpregnated glass fabric within these layers;

Figure ..6 is a cross-section of a screw-cap througha median line,showing with some eny largement the up-turned edge of the liner alongvthe internal periphery of the cap.

In further reference to the drawing, in Fig. 1, I illustrates a specimenof the mesh of the untreatedwoven glass fabric. In Fig. 2, 2 illustratesa specimen of the wax-impregnated glass fabric. In Fig. 3, l illustratesthe general overall `'smoothly waxed upper surface; 2, in the fragmentedcome;` illustrates the wax-impregnated glass fabric represented in Fig.2; 4 illustrates the inner aspect of the nether overall smoothly waxedsurface. In Fig. 4, representing a disproportionately perspective view,2. land I indicate the Vcorresponding parts 1n Fig. 3. In Fig. 5, 2, 3

l and 4 are indicated in enlarged sectional view.

In Fig. 6, i shows the liner composed of the material of Fig. 5positioned within the screw-cap 6. vIn this connection applicant hastested many weaves-oi? glass fabric, and he has found certain weavesparticularly suitablefto the accomplishment of his purpose. Forinstance, a desirable weave of glass fabric is composed of bers of whichabout 87 percent vary less than 20 percentfrom the average diameter of0.00025 inch. This glassber permits tight weaving and provides a strongall-glassfabric `which has the fol- -lowing characteristics, subject toreasonable `water pressure, for a fabric weighing 1.4 lbs. per

square yard..

- yWater porosity: Rate of flow of 286 gallons, per

minute, per square foot, under pressure across the fabric of lbs. ofwater per square inch.

that is soft and unctuous at ordinary tempera-4 tures is unserviceableand in fact objectionable in or upon screw-cap stopper seals because itdetaches itself by mere contact with container contents and contaminatesthem.

After testing many waxes, particularly with respect to their meltingpoints, fluidity, chemical inertness, odor, taste,'tenacity, etc., ithas been found, for example, that a wax which meets the followingspecifications is especially suitable for this purpose:

A wax having approximately the foregoing characteristics is sufiicientlyfluid at elevated temperatures, so that it can readily penetrate betweenthe fibers of the glass fabric, thus effectively wetting theirinter-faces and eventually affording the desired lubricating effect andclosure of the pores in the glass structure. When this wax cools, theindividual fibers of the glass, which normally lack insufficientlyserviceable flexibility, are buttressed by this inter-lubrication, sothat they cannot abrade one another, and upon the application ofscrew-cap pressure the wax protects the glass fibers from fracture bydistributing the stress throughout the lining material. At ordinarytemperatures this wax is tenacious, but not sticky, and is moderatelycompressible. As its particles do ,not break away during closurepressure, there is no physical contamination by wax of the contents ofcontainers. It is non-reactive to all the strong mineral acids. It doesnot discolor these acids. It has no deleterious effect on the materialof screw-cap closures. Its temperature range of utility, namely, 30 F.to 130 F., permits of the eflicient and safe use of applicants liningmaterialunder widely varying climatic conditions. Hence, the attainmentof the objective is critically dependent on the existence of the specialchemical and physical properties of the wax described and on its severalcoacting functions.

In the utilization of a wax having substantially these specifiedqualities, the success of its association with the described glassfabric has been found to depend on the adaption of certain optimumproportions of wax to glass, according to purpose. The determination ofthese proportions depends on the content of the wax essential for thelubrication and the buttressing of the glass fibers and for the sealingof the pores of the glass structure; the diameter of the glass bers andthe closeness of their weave; the size and thickness of the liner orgasket; the degree of corrosiveness and the volatility of the liquid orsubstance to be sealed; and, in the die-punching for producing theseals, the need of lubrication by the wax to prevent fracture and ruggedcontour of the liners or gaskets.

There must always be a sufficiency of the wax on the surface of thefinished product in order to ensure a tight sealing surface in contactwith the lip of the container without risk to the glass structure duringrepeated application of pressure of the screw-cap closure upon the rimof the containers neck. If the product contains insufficient wax theglass bers become exposed upon repeated loosening and tightening of theclosure. Such deficiency of Wax results in a glass to glass contact,which is not liquid-tight. On the other hand, an excess of wax upon thefinished product must be avoided because a liner that is unby thesurface arca of the given neness of the glass fibers in the glassstructure, by their thickness, by the type of weaving of the glassfibers,

by the fabrics mesh, by the nature of the wax, and by the dimensions ofthe screw-cap. This I ratio controls a critical limit above or belowwhich the lining material will not efficiently serve as a liquid-tightseal of screw-cap closures.

It has been found that the requisite range of proportions of thespecified wax to the described glass fabric is approximately 40`to 75percent of wax to 60 to 25 percent of glass, by weight. The optimum ofwax and glass contents .for the particular use can readily be determinedby those skilled in the art, having in mind the limitations andconsiderations as disclosed.

In the manufacture of applicants -lining material from the given tightlywoven glass fabric and the wax as described, the first step involves thecareful de-oiling or the de-greasing of the glass fabric. The wax willnot adhere firmly to an oily or greasy glass surface, or satisfactorilysheathe oily or greasy glass fibers. Moreover,

the removal of such contamination is an imporl tant precaution whereverthe discoloration of pure acids is to be avoided. Next, the cleansedrolls of glass fabric are impregnated and coated sealing properties,which remain perfect over a wide range of 4atmospheric temperatures andsuccessfully withstand the pronounced pressure which the liquid-tightclosing of the screw-caps entails.

It is obvious that certain modifications may be made in the steps of theprocess, and in the kind and proportions of the materials employed,without departing from the scope and spirit of the invention and thepurview of the claims.

1. A lining and sealing material comprising tightly woven glass fabricconsisting of fibers substantially averaging 0.00025 inch in diameterand affording resistance to air-flow and water-110W as indicatedrespectively by an air porosity characterized by an air velocity ofabout thirty cubic feet per minute, per square foot of fabric, under onelinch water pressure, for a fabric Weighing with the described wax, andfinally the finished about 1.4 lbs. per square yard, and by a waterporosity characterized by a rate of flow of about two hundred andeighty-six gallons per minute, per square foot, under pressure acrossthe fabric of about ten pounds of water per square inch,

- said fabric being substantially uniformly impreg- 2. An acid-proof andliquid-proof lining material comprising a tightly woven fabric composedof fine glass fibers substantially uniformly impregnated throughout witha wax having substantially the physical and chemical specifications asdened in claim 1, the wax filler being present in sufficient amount inrelation to the glass fabric to coat all the interfaces of the glass ffibers with a lubricant cushion and to ll the mesh spaces of the fabric.

3. An acid-proof and liquid-proof lining material comprising a tightlywoven fabric composedI of fine glass fibers substantially uniformlyimpregnated throughout with a wax having substantially the physical andchemical specifications as defined in claim 1, the wax ller beingpresent in sufficient amount in relation to the glass fabric to coat allthe interfaces of the glass fibers with a lubricant cushion, to fill themesh spaces of the fabric, and to form a thin illm thereof as anover-al1 coverage of the outer face of the thus wax-impregnated glassfabric.

ETI-IAN E. LAUER.

